This study intends to build on our knowledge of the consequences of alcohol and illegal drug use among adolescents entering adulthood. Specifically, it examines the effects of prior and current alcohol and illegal drug use on (1) the choice among cohabitation, marriage, and non-union parenthood as the first adult family form and (2) the timing of entry into adult family life. It aims to contribute to improving the quality, effectiveness, and efficiency of substance use prevention programs, chiefly those aimed at women and minorities during the initial family-building process. This study will employ at least five waves of the National Longitudinal Survey of Youth 1979 Young Adult data to examine the effects of alcohol and illegal drug use on first family formation for men and women; Blacks, Hispanics, and whites; and metro and non-metro residents. Multinomial logistic regression models are estimated to test whether alcohol and illegal drug use influences the choice of initial adult family form among all subjects and then within population subgroups. Nested models are estimated that include controls for childhood conditions and current characteristics of the young adults. Employing the same nested model design, discrete-time event history models are then estimated to test whether alcohol and illegal drug use affects the timing of first adult family formation among all subjects and then within population subgroups. Having children early or before marriage and getting married or romantically living with a partner for the first time at an unusually young or old age may cause harm to individuals, families, and society. If alcohol and illegal drug use matters to the choices people make about starting their families, it may contribute to poorer outcomes and lower well-being. [unreadable] [unreadable] [unreadable]